1. Technical field of the Invention
The present invention relates to a vehicular number plate including luminous characters and more particular, to a number plate including luminous characters which assures that character portions are more uniformly illuminated than a conventional one, has an excellent durability and can simply be produced with much easiness.
2. Description of the Related Art
A hitherto known number plate including luminous characters (hereinafter referred to as luminous number plate) is typically constructed as shown in FIGS. 1 and 2. Specifically, the number plate includes a case 1 to which an openable frame 2 is fitted. A number plate 4 coated with a paint having a certain specified color is attached to the frame 2 using set-screws 10. The number plate 4 has a plurality of character portion 3 punched therefrom to which symbols in the from of characters and numerals made of a transparent synthetic resin are adhesively secured. To illuminate the character portions 3 at night, illuminating bulbs 5 are disposed inside of the case 1.
With such conventional luminous number plate, the illuminated character portions 3 can be visually recognized from remote locations. However, it has been found that the conventional luminous number plate has a drawback that the respective character portions 3 are illuminated in a different manner such that the character portions located above the illuminating bulbs 5 are brilliantly illuminated but the character portions 3 located remote from the illuminating bulbs 5 appear dark.
To obviate the foregoing drawback, a translucent milkwhite light scattering plate 7 having black paints 6 (see FIG. 3) coated and baked in regions corresponding to the illuminating bulbs 5 while having a thickness gradually reduced toward the peripheral part thereof is interposed between the number plate 4 and the illuminating bulbs 5 (refer to an official gazette of Japanese Utility Model Publication No. 16,308/1978). In practice, a translucent milkwhite plate molded of polypropylene is used for the purpose of producing the light scattering plate 7. The reason why polypropylene has been used for it consists in that a synthetic resin having a high heat resistance should be employed so as to prevent an occurrence of malfunction that the material used for the light scattering plate 7 is discolored or softened under the influence of heat generated by the illuminating bulbs 5. As is well known, polypropylene has a degraded property of adhesiveness and moreover it is very difficult to secure a paint to polypropylene by a baking operation. To avoid this drawback, a light scattering plate having black-colored printed seals 6' adhesively secured thereto in regions corresponding to the illuminating bulbs 5 has been used. The printed seals 6' are such that they have a thickness gradually reduced toward the peripheral part thereof. However, it has been found that the improved light scattering plate 7 has still a drawback that the seals have a low strength against peeling and they are gradually deteriorated under the influence of heat generated by the illuminating bulbs until they are peeled away from the light scattering plate 7.
With such light scattering plate, it has been found that it has another drawback that a boundary 8 between the region where the black-colored paints 6 or the seals 6' are adhesively secured thereto by painting and baking and the region where any paint and sealing means are not provided appears such that the respective characters have stripes formed thereon.